BMW R1200 motorcycle engine

[rtfm]

Hi,
I know the received wisdom on auto conversions is that they are probably more trouble (and expense) than they are worth, and that one would probably be better off buying a regular aircraft engine and have done with it. But I have just come across the BMW R1200 engine, and I think this changes the rules somewhat.

As far as I can tell, the major obstacles standing the the path of any would-be auto (or bike) conversion wanna-be, are the difficulties of:

• finding a suitable gearbox
• Ensuring sufficient cooling in very tight cowl spaces
• sorting out the engine mount
• Beefing up the innards to withstand the extra operating stresses aircraft use puts on engines
• fiddling with the ignition (dual ignition almost mandatory)
• getting the computer to work without some of the sensors feeding info back to the CPU (most car sensors are not required for flight, and their absense confuses the CPU

It is probably no coincidence that the VW conversions are so popular in aircraft. They have no complicated CPU's to worry about, require no gearbox, are air cooled. Add to that a very simple basic design, and voila - a very suitable candidate for aircraft conversion.

But the modern generation of BMW motorcycle engines offer the home builder a great deal:

• Air cooled
• No complicated sensors to work around
• EFI
• Dual ignition
• Bolt-on gearboxes available (Rotax or Autoflight)
• No need to alter the innards at all.
• Over 100hp without modification

Guys who have converted the older R100 to aircraft use make no engine modifications at all - except possibly (and optionally) to polish the ports and fit an extra spark plug per cylinder. They fly them as-is.

The latest generation of BMW engines already come with dual ignition and EFI. Bolt on either the Rotax-C gearbox or the excellent Autoflight box, and you're about ready to go.

Weight? The R100 stripped of the unnecessary bits and with the gearbox already in place weighs in at 74kg. The Aerovee (VW conversion by Sonex) weighs 76kg and only produces 80hp.

Reliability? The BMW engine is virtually unbreakable.

Cost? One can buy a late model BMW motorcycle in great condition here in Auckland for about $8k NZD (about $5k USD). Add a couple of grand for the PSRU, and it is a pretty sweet deal.

Duncan

 

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